how to recognise handwriting and convert into text?
What you described sounds to me like Optical Character Recognition(OCR). 

If you want to implement your own, I would say read through how an open source OCR like Tesseract was implemented. 

Otherwise just google for OCR and you will find a list of OCR engines, both comercial and open-source. To list but a few: 


Tesseract: https://github.com/tesseract-ocr/tesseract
Matlab Computer Vision Toolbox's OCR: http://www.mathworks.de/de/help/vision/ref/ocr.html


Most OCRs makes use of a combination of a segmantation and image classification(usually done with Convolutional Neural Networks). 

See here for more information.